CHICAGO (Reuters) - A new, highly efficient material that converts
heat into electricity may one day help cars get the most out of a
gallon of gas, U.S. researchers said on Thursday.

Only about 25 percent of the energy produced by a typical gasoline
engine is used to move the vehicle or run accessories like the radio or
windshield wipers, they said. Much of the rest escapes through the
exhaust pipe.

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Researchers at Ohio State University in Columbus and Caltech in
Pasadena, California, think they can recycle some of that lost energy
with a new thermoelectric material that is twice as effective as
current materials.

"The material does all the work. It produces electrical power just
like conventional heat engines -- steam engines, gas or diesel engines
-- that are coupled to electrical generators, but it uses electrons as
the working fluids instead of water or gases, and makes electricity
directly," Joseph Heremans, who led the project, said in a statement.

Jeff Snyder of Caltech, who worked on the project, said a
thermoelectric device that converts heat from exhaust into electricity
could improve a car's fuel efficiency by 10 percent.

Snyder, who previously developed such devices for NASA's Jet
Propulsion Laboratory, said the idea of using thermoelectrics had been
around for a long time, but the economics did not make sense when oil
cost $20 a barrel.

"Now that energy costs have gone up by a factor of five, these
alternative ideas that have been around for awhile are a lot more
viable," Snyder said in a telephone interview.

He believes it would be possible to make the systems within the next five to 10 years.

Whether it catches on, Snyder said, will depend on the cost of the
system and the energy market. If made on a large scale, Snyder said it
might be possible to develop the systems for $10 a unit or less.

Currently, the most efficient material used commercially in
thermoelectric power generators is an alloy called sodium-doped lead
telluride, which has a rating of 0.71. By adding a bit of thallium to
the lead telluride, the researchers doubled the efficiency rating to
1.5.

Tests of the material found it might be ideally suited for use in
engines. They found that at near 450 degrees Fahrenheit (230 degrees
Celsius), the material converted heat to electricity at about the same
efficiency rating as currently available materials.

At higher temperatures, it became more efficient, hitting its peak
efficiency rating of 1.5 at 950 degrees F (500 degrees Celsius).

Between 450 degrees and 950 degrees Fahrenheit is about the typical range for power systems, such as car engines, Heremans said.

The researchers have applied for a patent and are refining the
material. The hope is to combine this finding with other recent
discoveries that may produce further improvements in efficiency.

Snyder said a thermoelectric device using the material would need to
be encased because thallium is highly toxic, but such devices could be
recycled. He said it might be possible to find another, nontoxic
thermoelectric system that shows the same kind of efficiency.